Performance

The Performance tool gives you insight into your site's general responsiveness, JavaScript and layout performance. With the Performance tool you create a recording, or profile, of your site over a period of time. The tool then shows you an overview of the things the browser was doing to render your site over the profile, and a graph of the frame rate over the profile.

You get four sub-tools to examine aspects of the profile in more detail:

the Waterfall shows the different operations the browser was performing, such as executing layout, JavaScript, repaints, and garbage collection

the Call Tree shows the JavaScript functions in which the browser spent most of its time

the Flame Chart shows the JavaScript call stack over the course of the recording

the Allocations view shows the heap allocations made by your code over the course of the recording. This view only appears if you checked "Record Allocations" in the Performance tool settings.